Angled PCB Contacts Prevent CAF Growth
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Solution Overview
Problem
The increasing pitch of electronic components has made Conductive Anodic Filament (CAF) growth a reliability concern for printed circuit boards, as the time for CAF to bridge features has decreased to within the system's life expectancy, leading to potential failures due to insufficient binding of resin to glass fibers, hollow glass fibers, and inadequate resin impregnation.
Innovation Solution
Fabricating printed circuit boards with component contacts angled relative to the glass fiber bundles, thereby lengthening the paths between contacts and minimizing the likelihood of CAF growth by ensuring adjacent contacts do not contact the same glass fiber bundle, which can be achieved by manufacturing panels with angled glass fibers or laying out components at an angle on traditional panels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the pitch between component contacts is reduced to accommodate tighter spacing, then the board can support more components, but the time for CAF growth to bridge features decreases to within system life expectancy
Solution Approach 1:
The patent applies dimensional change by rotating the component layout by 45 degrees relative to the glass fiber bundle orientation. This angular offset transforms the original alignment problem where contacts were positioned along the same glass fiber path into a configuration where adjacent contacts intersect different glass fiber bundles, effectively increasing the CAF growth path length despite reduced pitch spacing.
2Ease of manufacture
If traditional X-Y orthogonal layout is used for simplicity, then manufacturing and assembly are easier, but adjacent contacts align with the same glass fiber bundles creating CAF growth pathways
Solution Approach 1:
The patent introduces asymmetry by deliberately misaligning the component contact grid with the glass fiber bundle orientation. Instead of using the symmetric X-Y orthogonal layout that aligns with the weave pattern, the contacts are positioned at a 45-degree angle, creating an asymmetric relationship between the electrical pathways and the structural glass fibers that disrupts CAF growth channels.
Data Source
AI summary
A printed circuit board is fabricated so contacts for tight-pitch components are at an angle with respect to the bundles of glass fibers in the epoxy-glass printed circuit board such that adjacent component contacts do not contact the same bundle of glass fibers. This angle may be accomplished by manufacturing a printed circuit board panel with the glass fibers at an angle with respect to its edges. This angle may also be accomplished by placing parts on a printed circuit board panel that has a traditional X-Y orthogonal weave of glass fiber bundles at an angle with respect to the edges of the panel. This angle may also be accomplished by starting with a traditional panel that has an X-Y orthogonal weave, laying out parts on the panel along the X-Y weave, then placing components on the parts at an angle with respect to the edges of the parts.